1. Field of the Invention
The present invention relates to the field of vacuum sputtered coating apparatus and particularly relates to an improved sputtering process and apparatus, and more particularly, to the construction of an improved cathode/anode assembly which provides better utilization of and uniformity in the material deposited.
2. Description of the Prior Art
A typical magnetron sputtering device includes a vacuum chamber having an electrode contained therein, wherein the electrode includes a cathode portion, an anode portion, and a target. A vacuum is drawn in the vacuum chamber followed by the introduction of a process gas into the chamber. Electrical power supplied to the electrode produces an electronic discharge which ionizes the process gas and produces charged gaseous ions from the atoms of the process gas. The ions are accelerated and retained within a magnetic field formed over the target, and are propelled toward the surface of the target which is composed of the material sought to be deposited on a substrate. Upon striking the target, the ions dislodge target atoms from the target which are then deposited upon the substrate. By varying the composition of the target, a wide variety of substances can be deposited on various substrates. The result is the formation of an ultra-pure thin film deposition of target material on the substrate.
What is termed the electrode above (which includes both a cathode portion and anode portion) is sometimes simply called a cathode by those skilled in the art. While the inventor recognizes that convention, the discussion below does not follow this convention because calling the electrode a cathode will only cause confusion in the following discussion which discusses separately the cathode and anode portions of the electrode.
U.S. Pat. Nos. 5,736,019 and 6,171,461, which are incorporated herein by reference, disclose an attempt to overcome under utilization of target material via the use of stationary profiled magnets. The above-identified patents are directed to magnetron sputtering electrodes that include a plurality of profiled magnets, each magnet including a top portion with an apex, wherein each apex is positioned adjacent a target supporting surface in the cathode body. The magnets cooperate to generate magnetic flux lines which form enclosed-looped magnetic tunnels adjacent to the front sputtering surfaces of the targets. As described in the above-identified patents, these profiled magnets result in optimum utilization of target material at a reasonable rate of utilization.
Stationary magnet sputtering cathodes and target substrates only permit a portion of the target that can be utilized during the sputtering process. Prior art patents have disclosed rotating magnets for use in sputtering devices such as U.S. Pat. Nos. 5,252,194; 5,194,131; 5,188,717; 5,170,140; 4,756,815; and 4,714,516, which are incorporated herein by reference. A problem with these arrangements is that magnets have flat upper surfaces and therefore the target, which the material is to be sputtered from, is not completely utilized.
Therefore, it is an object of the present invention to increase the amount of target material that can be used during a sputtering process.